(Received 22 December 2008;accepted 18 February 2009;online 25 February 2009)

Mol­ecules of the title compound, C22H20N2O2, are situated on crystallographic centres of symmetry. The oxazinane ring adopts a sofa conformation. Mol­ecules are linked into cyclic centrosymmetric dimers via C—H⋯O hydrogen bonds with the motif R22(6). In addition to the C—H⋯O inter­actions, the crystal structure is also stabilized by C—H⋯π inter­actions.

Bis-benzoxazine compounds exhibit various biological activities including antibacterial ( i. a. tuberculostatic), antitumor, fungicidal and plant-growth regulative properties (Billmann & Dorman, 1963; Heinisch et al., 2002). Polyoxymethylene (paraformaldehyde) undegoes a bimolecular condensation with N,N-bis-(o-hydroxybenzyl)-ethylenediamine in benzene to form 1,2-bis-[3-(3,4-dihydro-1,3–2H-benzoxazino]-ethane, which shows bacteriostatic and fungistatic activities (Billmann & Dorman, 1963). Taking into consideration these aspects, and in order to obtain a detailed information on the molecular structure in the solid state, the X-ray structure determination of the title compound has been carried out.

The molecules are situated on the crystallographic centres of symmetry and therefore have symmetry 1 (Fig. 1). The bond lengths N1—C7, O1—C5 are normal and comparable to the corresponding values observed in the related structure of 1,4-bis(8-tert-butyl-6-methyl-4H-1,3-benzoxazin-3-yl)benzene (Huerta et al., 2006).

In addition to the van der Waals interactions, the crystal packing is stabilized by C–H···O and C–H···π hydrogen bonds (Tab. 1) as well as by π–π-electron interactions. The atom C8 acts as a donor to the atom O1 of the neighbour molecule. This hydrogen bond is involved in a motif C11(10) forming an infinite chain along b axis. C11(10) projected on the axis b corresponds to the translational period along this axis. Simultaneously a pair of C8–H8A···O1 hydrogen bonds form a cyclic centrosymmetric dimer [R22(6)]. The π–π-electron interactions between the rings (C1\C2···C6) at x, y, z and 1-x, -y, -z with the centroid-centroid distances equal to 3.780 (2) Å are observed in the crystal structure.

A mixture of 2-(4-[(2-hydroxybenzyl)amino]anilinomethyl)benzenol (0.005 mole) and methanal (0.010 mole) was irradiated under microwaves generated by IFB Microwave Oven (Frequency = 2450 MHz ~λ=122 mm; 480 W) for 4 to 6 minutes; the distance from the source to the sample was 15 cm. The progress of the reaction was monitored by a thin layer chromatography. After completion of reaction, ice-cold water (50 ml) was added to the reaction mixture and stirred. The title compound was extracted with chloroform, the combined organic layers were dried over anhydrous sodium sulfate and then the solvent was evaporated. The crude product was recrystallized in ethylacetate at room temperature. The elongated single cystals of the title compound of average length of 2 mm were grown.

All the H atoms could be clearly discerned in the difference electron density map. Nevertheless the atoms were situated into the idealized positions and refined in the riding model approximation. The constraints: Caryl-H = 0.93 and Cmethylene-H = 0.97 Å. UisoH=1.2Ueq(Caryl/methylene).

Fig. 1. View of the title molecule with the atom labelling scheme. The displacement ellipsoids are drawn at the 30% probability level while the H atoms are shown as small spheres of arbitrary radii.

Fig. 2. The crystal structure showing the centrosymmetric hydrogen bond motif R22(6). For the sake of clarity, the H atoms not involved in the motif have been omitted. The atoms marked with an asterisk (*) are situated in the position (2-x, 2-y, -z). The dashed lines indicate the hydrogen bonds.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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